The speaker assembly is an important component in the display device. The max sound pressure level (max SPL) of one speaker assembly is positively related to the volume of the speaker assembly. However, if the volume of one speaker assembly is increased, the volume or the thickness of the display device utilizing the speaker assembly will be increased as well. Hence, how to increase the max SPL of one speaker assembly without increasing the volume thereof, or how to maintain the max SPL of one speaker assembly while decreasing the volume thereof is a problem to be solved.